The present invention relates to a method for the production of PIR/PUIR/PUR foam cored sandwich panels with metal sheets as facings at top and bottom. The present invention further relates to an apparatus for the production of PIR/PUIR/PUR foam cored sandwich panels with metal sheets as facings at top and bottom.
Such sandwich panels are produced in continuous double belt line. With this production process, the upper metal sheet and the lower metal sheet are continuously fed into a double belt. An adhesive is applied to the lower metal sheet and, subsequently, the foam core material is dispensed between the upper metal and the lower metal sheet. With this process, the adhesion of foam to the lower metal sheet is improved and it provides a very strong foam adhesion to the lower metal sheet. However, the adhesion of the foam to the upper metal sheet is dependent on the formulation of the foam material, the metal sheet temperature, the type of coating on the metal inner surface and application of corona treatment to metal sheets. Generally, the adhesion of foam to the upper metal sheet is weaker compared to the adhesion of the foam to the lower metal sheet, where the foam-metal-bonding strength is much stronger due to the adhesive actually being applied to the lower metal sheet.